Users become stronger, faster, more durable, etc. when they come in contact with crystals and gemstones, possibly unlocking abilities related to the affinity and enhancing the existing powers. Some users may be able draw sustenance from them or even slow or stop aging.
When armed with the infinity gems, Infinity Gauntlet (Marvel Comics) gives the wearer cosmic control of the universe.
Powered by the infinity stone of the mind, the Chitauri Scepter (Marvel Cinematic Universe) allows the wielder to control the minds of others, making them their obedient slaves.
Vision (Marvel Cinematic Universe) is powered by the infinity stone of the mind.
Powered by the infinity stone of time, the Eye of Agamotto (Marvel Cinematic Universe) is a powerful magical artifact created by the sorcerer supreme Agamotto with the power to manipulate time.
Thanks to his Semblance to block out pain, Hazel Rainart (RWBY) can infuse raw Dust crystals into his body in order to increase his strength and grant him elementally enhanced strikes depending on the type of Dust he uses.
Saint-Germain, Cagliostro , Prelati (Senki Zesshou Symphogear AXZ) used philosoper stones in the form of gemstones to clad themselves in powerful alchemical armours called Faust Robe.